Edh general rule

[An Angry Fatman]

Let's say my general is out when my opponent plays a {terminus} does he go back to general spot?

[Keyeto]

No. They can only go back to their command zone if destroyed or exiled. All other cases (put in library, returned to hand, etc) are treated normally.

From the Comprehensive Rules:

903.11. If a commander would be put into its owner's graveyard from anywhere, that player may put it into the command zone instead.

903.12. If a commander would be put into the exile zone from anywhere, its owner may put it into the command zone instead.

[An Angry Fatman]

So you can't oblivion ring a general? it would go back to it's zone?

[Keyeto]

So you can't oblivion ring a general? it would go back to it's zone?

Only if that player chooses to put it in the command zone. They may choose not to.